1. Field of the Invention
The present invention relates to a method of manufacturing piezoelectric ceramic composites for devices, for example transducers and sensors. More particularly, the present invention relates to a method for manufacturing a piezoelectric ceramic body for piezoelectric ceramic-polymer composites.
2. Background Art
Piezoelectric composites have been used, with increasing frequency, in acoustic transducers for ultrasonic imaging, biometrics, and non-destructive testing (NDT). Typically, the acoustically active element in such transducers is made from piezoelectric ceramic materials. However, market demand for large array acoustic transducers has been inhibited by the high costs involved in manufacturing the piezoelectric composites. The high cost is largely due to difficulties in the manufacturing processes associated with fabricating the ceramic bodies for the transducers.
The most common fabrication method for manufacturing piezoelectric composites for transducers is the dice and fill (D&F) method. In the D&F method, a wafer saw is used to cut a grid of rectangular or rhombic shaped kerfs into a sintered piezoelectric ceramic body without cutting all the way through (i.e. leaving a solid material base). The kerfs are then filled with a polymer; a process known as encapsulation. This method produces a matrix of ceramic pillars surrounded by a polymer fill. Further processing to fabricate a transducer or sensor continues by grinding away any unslotted sections of the ceramic body, electroplating the surfaces of exposed ceramics, machining to shape and poling.
However, the D&F method has several limitations. One such limitation is that the D&F method costs about $100-$200 per square inch depending on the frequency and associated pillar pitch of the transducer. Additionally, due to the hardness of the piezoelectric sintered ceramic body, the processing time is consuming; can only dice at a speed of about 3 mm/sec to 5 mm/sec. Further, dicing utilizes thin diamond coated blades to slot (cut) the ceramic body. The blades are expensive, have short usage lives, and are difficult to change.
What is needed, therefore, is a more efficient and lower cost method for reliably manufacturing piezoelectric ceramic bodies for fabricating piezoelectric composites for large array acoustic transducers and sensors. Also needed is a method and/or system to improve shrinkage control and reduce warpage. Controlling shrinkage allows for more efficient processing of a sintered ceramic body for fabrication of transducers and sensors.